The present invention relates to the technical field of electronic devices of the contactless type comprising a near-field communication antenna for establishing communication with an external reader or possibly even read/write terminal.
Such devices are generally portable and wireless and are able to exchange data with the terminal by electromagnetic coupling.
The invention also applies to any type of portable or pocket electronic device incorporating such an antenna, such as a USB key, RFID (for Radio Frequency IDentification) tag, etc.
The invention applies more particularly but not exclusively to microcircuit cards equipped with an antenna, such as the so-called contactless cards allowing communication to be established without contact at a predefined communication frequency, for example the 13.56 MHz frequency defined by the ISO 14443 standard.
It also applies to so-called hybrid or dual cards which allow the establishment, in addition to contactless communication, of communication using contact through an external contact interface capable of making contact with a matching reader.
Generally, the device lacks an independent power supply. For its electrical power supply, the microcircuit includes two input terminals each connected to one of the ends of the antenna: to operate, it uses the magnetic field emitted by the external terminal. Thus, when the device is within the magnetic field of the terminal, a high-frequency voltage, called the supply voltage, is generated at the terminals of the microcircuit.
Generally, the supply and communication frequencies are distinct so as to avoid undesired interference which might harm the quality of the exchanged signals.
It is desirable to reduce the dimensions of the antenna to facilitate its incorporation into small platforms, such as for example a mobile telephone network identification card, also called a SIM card, in the ID-000 format.
The invention relates more particularly to cards or to portable electronic devices in which it is desired to reduce the dimensions of the antenna while still maintaining performance, particularly its range, that is the maximum distance between the portable electronic device and the reader that allows a communication session to be established.
To compensate for the reduction in performance of the antenna connected with the reduction in the effective area of the latter, it is generally known to incorporate an antenna gain amplifier into the substrate.
A chip device comprising an antenna connected to the chip and an antenna gain amplifier comprising a second antenna physically separate from the first antenna is known in the state of the art, particularly in the international application published under the number WO 2009/122010. In this document, the second antenna is arranged near the first antenna to allow energy transfer by coupling between the antennas.
As stated in this document, the second antenna allows improvement of the performance of the first antenna and thus to noticeably increase the latter's communication distance.